I understand that in Ran-dependent nuclear import Ran GTP binds importin in the nucleus, and after diffusing through the nuclear pore complex Ran GTP is hydrolyzed to Ran GDP and releases importin. How does the hydrolyzed Ran GDP get from the cytoplasm back through the nuclear pore complex to the nucleus? The same question applies to nuclear export after Ran GTP is hydrolyzed following export of the Ran GTP-exportin-cargo complex. Does Ran GTP freely diffuse through the nuclear pore complex? Is it actively transported?